As an electronic countermeasures (ECM) technique, it has been known to produce slowly changing false doppler frequencies by a so-called velocity gate stealer (VGS). Such apparatus, for example, might be mounted in an aircraft and would receive a radar pulse from the ground which is operating on the doppler system and then would pull the velocity tracker of the ground radar off the target return to drop it. The radar may then lock on the clutter or be forced into a reacquisition sequence.
A common implementation of the foregoing is a serrodyne technique utilizing a traveling wave tube (TWT). Serrodyning is, of course, phase modulation using the transit time modulation of a traveling wave tube. In practice, a voltage in the shape of a sawtooth waveform is impressed on the helix of the TWT to provide the desired phase shift.
Since the foregoing is most used in aircraft on aerial targets, weight, of course, is a critical factor.
Thus, it is an object of the invention to provide an improved velocity deception apparatus and more particularly one which is of relatively light weight but with significant control flexibility.